Venturi dual flow filters are described and claimed in U.S. Pat. No. 6,478,958, assigned to the assignee of the present invention. Those filters have the desirable characteristic of filtering all of the oil through a primary filter, then filtering a predetermined percentage of the oil through a secondary higher density filter. A venturi tube is used to provide a passageway for all of the flow of filtered fluid back to the engine. The majority of flow in the passageway is passed through the primary filter only. The size and positioning and characteristics of the venturi in the tube, along with the flow rate, determines the percentage of oil which is brought through the secondary filter and the venturi port to join with the primary flow back to the engine.
Filters of this type, while presenting useful filtering advantages, can present a disposal problem. Due to ease of installation, many applications prefer the spin-on cartridges disclosed in the aforementioned patent. These have a metal outer case, a metal baseplate, and other metal components within the filter. Even if replaceable cartridges were utilized, they also have significant metal components, often in the form of centertubes or support grids for supporting the filter element, and metal endcaps for sealing the ends of the filter and maintaining relative position of the components. Thus, significant elements of filters of this type will not burn, preventing the use of incineration for relatively complete disposal of the spent filters or filter cartridges.